Field of the Invention
The present invention relates to an ignition coil for an internal combustion engine. More specifically, the present invention relates to an easy-to-produce and low-cost ignition coil for an internal combustion engine.
FIG. 6 shows a cross sectional view of an ignition coil for an internal combustion engine, while FIG. 7 shows its plan view. In the figures, a core 1 is a core of closed magnetic circuit type which goes through a coil body as described later. A primary bobbin 2 is arranged so as to encircle a part of said core 1. On the outskirts of the primary bobbin 2, a primary coil 3 as a conductive wire is formed so as to wind around the core 1. Low voltage terminals 4a and 4b are arranged on a case 9. One end of said primary coil 3 is connected to said terminal 4a, while the other end of said primary coil 3 is connected to said terminal 4b.
On the outskirts of said primary coil 3, a secondary bobbin 5 is arranged so as to encircle said core 1 and said primary bobbin 2. On the outskirts of said secondary bobbin 5, a secondary coil 6 is formed so as to wind around said core 1 and said primary bobbin 2, and a conductive wire of, for example about 100 times the number of turns of said primary coil 3, is wound around. Arranged on said secondary bobbin 5 are terminals 7a and 7b, to which both the ends of said secondary coil 6 are respectively connected. Said primary coil 3 is also connected to said terminal 7a. Said primary bobbin 2 and said secondary bobbin 5 are contained in said case 9, and a resin material 8 is mounted on said secondary bobbin.
An opening end 9a to take out high voltage is arranged at said case 9, and a high voltage terminal 10 made of a conductor is mounted within this opening end 9. One end of said high voltage terminal 10 is thread-cut, while the other end is cylindrical, and a spring 11 is contained in its inside.
As shown in FIG. 8 and FIG. 9, an intermediate conductor 12 as a supporting material is mounted on said resin material 8, and one end of an electronic circuit device 13 is electrically connected to a terminal 12a arranged at said intermediate conductor 12, while the other end of an electronic part 13 is electrically connected to a terminal 7b arranged at said secondary bobbin 5. A lead 13a of said electronic circuit device 13 is wound around or hooked to said terminal 12a and terminal 7b, and then electrically connected by means of soldering. This electronic circuit device 13 has a role to prevent the voltage generating at the start of electricity flow into the primary side from outputting. Respective components contained within said case 9 are fixed and insulated by an insulating resin 14 as an injection resin such as epoxy resin or so.
The ignition coil engine described above operates as shown below. Namely, when electricity is supplied from said external device not shown in the figure via said terminals 4a and 4b to said primary coil 3, said primary coil 3 generates magnetic flux, which runs through said core 1 and crosses said secondary coil 6. After a lapse of a certain amount of time, if the electricity to said primary coil 3 is shut down, magnetic flux that has crossed said secondary coil 6 decreases rapidly. Then, according to the principle of electromagnetic induction, this flux change generates high voltage in proportion with the number of turns of said primary coil 3 and said secondary coil 6. Next, high voltage generated is output via said electronic part 13, said intermediate conductor 12, said high voltage terminal 10, and said spring 11.
In the ignition coil for an internal combustion engine as described above, there have been problems, for instance, in that it is difficult to hook the lead wire of the electronic circuit device on a connecting point or wind it around by means of soldering, and in that soldering near the coil causes solder spatter to the scatter to coil, resulting in possible short-circuiting within the coil. Also in order to seal the opening portion for high voltage, the case wall is pinched from the outside and the inside, therefore, a high pressure terminal is needed in addition to an intermediate conductor, thus increasing the number of parts. Furthermore, there is also the problem that the sharp cut face of the lead wire end portion of the electronic part in contact with an insulating resin causes cracks in the insulating resin.